OLED Pixel Circuit Hysteresis Threshold for Leakage
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Solution Overview
Problem
In OLED displays, the voltage transmitted to the gate electrode of a driving transistor is not maintained constant due to leakage currents and noise, leading to non-uniform luminance in images displayed.
Innovation Solution
A pixel circuit is designed with a threshold circuit having a hysteresis characteristic, including a first transistor connected to a data line and a second transistor connected to an organic light emitting diode (OLED), where the threshold circuit outputs low-level or high-level voltages based on input signals to control the current flowing to the OLED, effectively preventing the influence of leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional pixel circuit is used, then the circuit structure is simple, but the voltage at the gate electrode of the driving transistor cannot be maintained constant due to leakage current
Solution Approach 1:
A threshold circuit is introduced as an intermediary component between the data line and the driving transistor gate electrode. This threshold circuit converts the input voltage signal into a stable output voltage that drives the gate electrode, effectively isolating the gate from leakage current effects and maintaining voltage stability without requiring fundamental changes to the overall pixel circuit architecture.
Solution Approach 2:
The pixel circuit is divided into distinct functional segments: a data input stage, a threshold circuit stage, and a driving transistor stage. By segmenting the circuit, the threshold circuit can specifically address the voltage stability issue at the gate electrode without affecting other parts of the circuit, allowing independent optimization of each segment's function.
2Reliability
If the threshold circuit is added to maintain voltage, then the voltage stability is improved, but the circuit complexity increases
Solution Approach 1:
The threshold circuit is designed to perform multiple functions simultaneously: it stabilizes the gate voltage, compensates for leakage current effects, and ensures uniform luminance output across all pixels. By making this single circuit element multi-functional, the need for multiple separate components is reduced, thereby limiting the increase in overall circuit complexity while achieving multiple performance improvements.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution maintains a constant voltage at the gate electrode of the driving transistor, ensuring uniform luminance in images displayed by the OLED display.
Implementation Method 1
the threshold circuit has a hysteresis characteristic with respect to the input signal
Implementation Method 2
an organic light emitting diode (OLED), where the second transistor controls a current amount which flows to the OLED from the driving voltage
Data Source
AI summary
A pixel circuit includes: an organic light emitting diode (“OLED”); a threshold circuit which generates an output signal based on an input signal, where the threshold circuit has a hysteresis characteristic with respect to the input signal; a first transistor including a first electrode connected to a data line, a second electrode connected to an input terminal of the threshold circuit, and a gate electrode connected to a scan line; and a second transistor including a first electrode connected to a first power, a second electrode connected to an anode of the organic light emitting diode, and a gate electrode connected to an output terminal of the threshold circuit, where the second transistor controls a current amount that flows to the organic light emitting diode from the first power based on the output signal of the threshold circuit.